1. Technical Field
The present invention relates to a sensor unit, and an electronic apparatus and a moving object including the sensor unit.
2. Related Art
In the related art, a sensor unit is known in which a substrate on which a sensor device including an inertial sensor, such as an acceleration sensor or an angular velocity sensor, which is resin-sealed by a sealing resin, and other electronic components are mounted is accommodated in a case member including a lid member such that at least the sensor device is covered by the lid member. The sensor unit is incorporated into various electronic apparatuses or machines or mounted in a moving object such as an automobile, and is used to, for example, perform the monitoring of the amount of inertia such as acceleration or angular velocity. Here, when external vibration or impact exceeding a predetermined intensity is applied to the sensor unit, or when external vibration or impact is applied thereto for more than a predetermined time, an inertial component of the vibration or impact is superimposed on the vibration of the inertial sensor, and thus the detection accuracy for the amount of inertia is reduced.
As a sensor unit capable of solving such a problem, for example, JP-A-2006-153799 shows a sensor unit having a configuration in which a substrate on which a sensor device is mounted is supported to a case member (package) through an adhesive member (adhesive) and the sensor device mounted on the substrate is covered by the adhesive member. For the adhesive member, a material whose modulus of elasticity, thermal conductivity, and dielectric constant can be reduced after solidification is used. With this configuration, propagation of the external vibration or impact, heat, or an electromagnetic wave to the sensor device (inertial sensor) is suppressed, and thus it is possible to suppress a reduction in the detection accuracy for the amount of inertia.
In the sensor device, the present inventor has found that, in addition to the problem described above, even when the sensor device is returned to a normal temperature after being exposed to a high temperature environment, the detected value of the amount of inertia continues to change, and thus the detection accuracy is reduced in some cases. The present inventor has found that the reasons for this are that the substrate, the sensor device (sealing resin), and the case member including the lid member are deformed due to thermal stress when heated to a high temperature, and differences occur, when returned to a normal temperature, in the return of the members from the deformation due to the thermal stress because of differences among linear expansion coefficients of the respective members, and that since the deformation (return) of the members continues for a predetermined time after the members are returned to a normal temperature, stress continues to be applied to the sensor device (inertial sensor) and thus affects a change in the detected value of the inertial sensor over time.
In the configuration of the sensor unit disclosed in JP-A-2006-153799, the adhesive member supporting the substrate on which the sensor device is mounted in the case member and covering the sensor device mounted on the substrate is not connected to the inner wall of the case member due to the presence of a space between the inner wall of the case member and the adhesive member. Therefore, there is a problem in that after the members are returned to a normal temperature after being exposed to a high temperature environment, it may be impossible to suppress the change in the detected value of the amount of inertia over time caused by the occurrence of thermal stress in the members.